Helical polyacetylene was synthesized under an asymmetric reaction field consisting of chiral nematic (N*) liquid crystals (LCs). The chiral nematic LC was prepared by adding a chiroptical binaphthol derivative as a chiral dopant to a mixture of two nematic LCs. Acetylene polymerizations were carried out using the catalyst titanium tetra-n-butoxide-triethylaluminum dissolved in the chiral nematic LC solvent. The polyacetylene film was shown by scanning electron microscopy to consist of clockwise or counterclockwise helical structure of fibrils. A Cotton effect was observed in the region of the pi --> pi* transition of the polyacetylene chain in circular dichroism spectra. The high electrical conductivities of approximately 1500 to 1800 siemens per centimeter after iodine doping and the chiral helicity of these films may be exploited in electromagnetic and optical applications.
A series of crown ether type binaphthyl derivatives (CEBDs) were synthesized and used as chiral dopants to induce chiral nematic (N*) liquid crystals (LCs). The twisting powers of the CEBDs for phenylcyclohexane (PCH)-derived nematic LCs were evaluated. It was found that the twisting powers of the CEBDs increased with decreasing ring size of the crown ether. Helical polyacetylenes were synthesized in the N*-LCs induced by the CEBDs. The relationship between the morphology of the helical polyacetylene and the helical structure of the N*-LC was investigated. The result showed that the interdistance between the fibril bundles of the helical polyacetylene was equal to a half-helical pitch of the N*-LC and the screw direction of the polyacetylene fibrils was opposite to that of the N*-LC.
The orientational distribution of cellulose nanocrystals (CNCs) in a cellulose whisker (CW) was investigated by means of the X-ray diffraction of magnetically oriented samples of CWs. A cellulose sample (Whatman CF11) was hydrolyzed and fractionated to prepare three different CW samples with a size ranging from ca. 10 to 100 μm. Each of the fractions that were suspended in a liquid matrix was aligned under a static or a rotating magnetic field, and the matrix was solidified to prepare magnetically oriented microcrystal arrays (MOMAs). Then, the MOMAs were investigated by X-ray diffraction measurements. By analysis of the diffraction patterns, it is concluded that the c-axes of the CNCs are uniaxially distributed within a CW and that the orientational order increases with decreasing CW size. The average anisotropic magnetic susceptibility ⟨χ a ⟩ of the CWs was expressed in terms of their size and of the X-ray azimuthal half width. Using these expressions, a correlation length for the orientation of CNCs in a CW was determined. The proposed method enables one to investigate the orientational order in a macrofiber at arbitrary scales by magnetically aligning the small fragments segmented from the macrofiber.
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